Five civilians were killed by bombs that "fell on their homes" in Khartoum, a Sudanese medical source told AFP, a day after an air strike in the city's south killed at least 20 civilians.

Residents of the war-torn capital reported the city was again pummelled by artillery and rocket fire Sunday, in the fifth month of war between the army and paramilitary fighters.

"The death toll from the aerial bombardment" in southern Khartoum late Saturday "has risen to 20 civilian fatalities", according to a statement from the neighbourhood's resistance committee. They are among many volunteer groups that used to organise pro-democracy demonstrations and now provide assistance to families caught in the line of fire.

In an earlier statement, they said the victims included two children, and warned that more fatalities went unrecorded, as "their bodies could not be moved to the hospital because they were severely burned or torn to pieces in the bombing".

Since war began between the regular army and the paramilitary Rapid Support Forces on April 15, around 5,000 people have been killed, according to conservative estimates from the Armed Conflict Location & Event Data project.

The Sudanese Armed Forces control the skies and have carried out regular air strikes while RSF fighters dominate the streets of the capital.

Western countries have accused the paramilitaries and allied militias of killings based on ethnicity in the western Darfur region, and the International Criminal Court has opened a new probe into alleged war crimes.

The army has also been accused of abuses, including a July 8 air strike that killed around two dozen civilians.

More than half of Sudan's 48 million people now require humanitarian aid and protection, and six million are "one step away from famine", according to the United Nations.

Despite insecurity, looting and bureaucratic obstacles, the world body says it has been able to get aid to millions of those in need.

The war has internally displaced around 3.8 million people, the UN says, while another million have crossed borders into neighbouring countries.

Among the displaced are nearly 2.8 million from Khartoum, according to the International Organization for Migration. That is more than half the capital's pre-war population of around five million.

Those who remain shelter from the crossfire, rationing water and electricity.

In Khartoum, resistance committees have been some of the only sources of relief, helping dig survivors out of the rubble of bombed buildings, braving gunfire on the streets to deliver medicine and documenting atrocities committed by both sides.

Nearly five months in, the violence shows no signs of abating.

Witnesses on Sunday again reported the army targeting RSF positions in northern Khartoum with "artillery and rocket fire".